A ninth grade math problem, about quadratic function. Master stamp Given that the sum of the reciprocal abscissa of the image of quadratic function y = 2x & sup2; - mx-4 and the two intersection points of X axis is 2, then M= I will use the Veda theorem, so, my dear friends, the first one to answer is to choose.

A ninth grade math problem, about quadratic function. Master stamp Given that the sum of the reciprocal abscissa of the image of quadratic function y = 2x & sup2; - mx-4 and the two intersection points of X axis is 2, then M= I will use the Veda theorem, so, my dear friends, the first one to answer is to choose.

The intersection point is set as X1 x2
Then 1 / X1 + 1 / x2 = x1x2 / (x1 + x2)
Weida theorem X1 + x2 = m / 2 x1x2 = - 2
So 1 / X1 + 1 / x2 = x1x2 / (x1 + x2) = - 4 / M = 2
So m = - 2

Given that the image opening of quadratic function f (x) = AX2 + (A2 + b) x + C is upward, and f (0) = 1, f (1) = 0, then the value range of real number & nbsp; B is ()
A. (−∞，−34]B. [−34，0)C. [0，+∞）D. （-∞，-1）

Because the image opening of quadratic function f (x) = AX2 + (A2 + b) x + C is upward, so a > 0. Because f (0) = 1, f (1) = 0, the solution is b = - a2-a-1. That is, B = - (a + 12) 2 − 34, (a > 0), so the range of B is (- ∞, - 1). So D

Solution: given that the parabola and X axis intersect at two points a and B, a is on the left side of B, the area of a coordinate (- 1,0) and Y axis intersecting at point C (0,3) △ ABC is 6
The symmetric axis of the parabola intersects with the straight line BC at point m, and point n is a point on the X axis. When the triangle with m, N, B as the vertex is similar to △ ABC, please find out the length of BN;
Here is the analysis
The axis of symmetry of the parabola is a straight line x = - B2A = 1,
From B (3,0), C (0,3), the analytic formula of the straight line BC is y = - x + 3;
∵ the axis of symmetry x = 1 intersects the line BC: y = - x + 3 at point M,
(1,2);
Let the length of BN be an unknown number
Let n (T, 0), when △ MNB ∽ ACB,
∴BNBC=MBAB
That is, 3-t32 = 224, that is, t = 0,
When ∵ MNB ∽ cab, bNAb = mbcb & # 8658; 3-t4 = 2232
T = 13,
So the length of BN is 3 or 83
I calculate t = 0 myself, why do I calculate t = 0 BN = 3 / 8
I calculate t = 0, why do I calculate t = 0 BN = 3 / 8

The answer is 3 or 8 / 3. There is no need to calculate the value of T in the middle. When △ MNB ∽ ACB, the corresponding edge is proportional to calculate the value of BN = 3. When △ MNB ∽ cab, BN = 8 / 3

If you only know the two intersections of the analytic expression and the x-axis, how can you find the axis of symmetry? For example, if you know that the two intersections of the analytic expression and the x-axis are 1 and 3, how can you find the axis of symmetry?

We can get y = a (x-1) (x-3)
Substitute another point to find a value
I don't know how to ask